System for distributing steam into resuperheaters



Aug. 23, 1960 A. BUR! SYSTEM FOR DISTRIBUTING STEAM INTO RESUPERHEATERS Filed June 22, 1956 3 Sheets-Sheet 1 INVENTOR. A LFIPED Bww.

ATTGEWEYS.

A. BURI 2,949,896

ESUPERHEATERS Aug. 23, 1960 SYSTEM FOR DISTRIBUTING STEAM INTO R Filed June 22, 1956 3 Sheets-Sheet 2 |||Il|||||li INVENTOR. A 1. FR :0 Hum.

Br ATTORNEYS- Aug. 23, 1960 A. BURI 2,949,896

SYSTEM FOR DISTRIBUTING STEAM INTO RESUPERHEATERS Filed June 22, 1956 3 Sheets-Sheet 3 INVENTOR. ALF/FED Bax/e1.

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SYSTEM FOR DISTRIBUTING STEAM INT RESUPERHEATERS Alfred Buri, Winterthur, Switzerland, assignor to Sulzer Freres, S.A., Winterthur, Switzerland, a corporation of Switzerland Filed June 22, 1956, Ser. No. 593,139

3 Claims. (Cl. '122-'-'479) The present invention relates to a system for distributing steam into at least three individual resuperheaters which are arranged in parallel relation with respect to the flow of steam therethrough and which are individually combined with and heated by the same heating agent as steam generators which are arranged in parallel with respect to the flow of water and steam therethrough.

In the system according to the invention the amount of steam directed into the resuperheater which is combined with the steam generator or boiler which'produces more steam than any of the other steam boilers is increased by throttling the steam flowing through the resuperheater-s which are combined with the other, less loaded, boilers. In a preferred embodiment of the invention the steam is so distributed into the resuperheaters that the ratio of the steam flowing through an individual resuperheater to the steam produced by the contiguous boiler is equal to the ratio of the total amount of steam flowing through all resuperheaters to the total amount of steam produced by all boilers.

The system according to the invention includes throttle means for each resuperheater, and actuating means for the throttle means which actuating means are responsiveto the output or rate of operation of the steam boilers WhlCh are not contiguous to the resuperheater into which the flow of steam is controlled. The actuating means include means which are responsive to and interrelate the operation of the individual actuating means so that the throttle means of the resuperheater combined with the steam boiler which produces the relatively greatest amount of steam is fully opened irrespective of the absolute amounts of steam produced by the contiguous steam boiler and by the other steam boilers.

The throttle means may be arranged at the outlet or at the inlet of the steam resuperheaters. Each steam boiler is provided with a control means which is responsive to the amount of steam produced by the steam boiler, i.e., which is responsive to the amount of water flowing into the steam boiler, to the water level in the steam boiler, or to the amount of steam leaving the boiler. Each boiler control means is connected with and actuates a pilot valve for controlling the flow of a pressure fluid into and out of a steam distributing device. The latter are parts of control units individually connected with the throttle means and are preferably in the form of a stepped piston reciprocating in a correspondingly shaped cylinder whose number of steps is one less than there are resuperheaters and steam boilers. The steps of the piston of the control unit of one superheater are individually supplied with pressure fluid controlled by the pilot valves which are actuated by the control means pertaining to boilers with which the other resuperheaters are combined. Each step piston is provided with a trunk portion which forms a pilot valve controlling the flow of a pressure fluid to and from an actuating piston or servomotor for the respective throttle means. The pressure of fluid whose flow is controlled by the trunk portion acts on the respective step piston in the same direction as the pressure acting on the 2,949,896 Patented Aug. 23, 1960 steps of the step piston. On the opposite side of each step piston acts a fluid pressure which is the same for all step pistons and which is made dependent on the total amount of steam produced by all steam boilers. In a preferred embodiment of the invention the active surfaces of the individual steps of the step pistons are all alike and the pressures produced by the pilot valves forming part of the step pistons are in proportion to the ratio of the output of the respective boilers to the output of the boiler operated at the relatively greatest rate of operation. The step piston associated with the boiler operated at the greatest rate of operation preferably produces by the pilot valve a pressure which is suflicient for fully opening the respective throttle means irrespective of the rate of op-- eration of the individual boilers. This is done by con-- trolling the pressure acting on the step pistons in a direc-- tion opposite to the pressure produced by the pilot valves connected with the step pistons and opposite to the pressures acting on the steps of the step piston. This control is performed by compensating pilot valves which are individually actuated by the pressure fluid controlled by the pilot valves of the step pistons. The compensating pilot valves are interposed in series relation in a compensating: pressure fluid supply conduit supplying pressure fluid of the same final pressure to all step pistons. The compen-- sating pilot valve pertaining to the highest loaded boiler is in neutral position, interrupting flow of pressure fluid to one side of the step pistons as long as the pilot valve connected with the step piston pertaining to the highest loaded boiler produces the relatively greatest pressure of the pressure fluid for fully opening the respective throttle means. The compensating pilot valves pertaining to the less loaded boilers are in a position permitting flow through the compensating pressure fluid conduit. Thecompensating pilot valves may be so constructed that the pilot valve pertaining to the highest loaded steamboiler admits fluid into the compensating pressure fluid conduit when the respective step piston moves out of its neutral position so that the compensating pressure tends to move the step piston in a direction in which its pilot valve increases the flow of pressure fluid for opening the associ ated throttling means. This increased pressure will return the compensating pilot valve to neutral or closing position. Alternatively, the compensating pilot valves may be so constructed that the pilot valve pertaining to the highest loaded boiler relieves fluid from the compensating pressure fluid conduit when the respective step piston moves out of its neutral position so that the compensating pressure tends to move the step piston so that its pilot valve decreases the flow of pressure fluid for opening the asso ciated throttling means. In this case the actuating means for the throttle means are so constructed as to open the throttle means upon decreasing fluid pressure. The decreasing pressure of the pressure fluid will return the compensating pilot valve to neutral or closing position.

A return mottion pilot valve is preferably inserted in the fluid pressure conduit controlled by the pilot valve which is part of a step piston, which conduit will hence"- forth be called the main pressure fluid conduit. The return motion pilot valve is actuated through a cam by the movement of the throttle means or of the servomotor moving the throttle means. The cam is so shaped as to coordinate the effect of the return motion pilot valve to the flow resistance in the respective resuperheater so that the ratio between the amount of steam flowing through the resuperheater and the amount of steam produced in the respective boiler is equal to the ratio between the total amount of steam flowing through all resuperheaters and the amount of steam generated in all boilers. V.

The servomotors actuating the throttle means for the resupe-rheaters in the system according to the invention are preferably also made responsive to the temperature and/or pressure of the steam in or leaving the resuperheaters. For this purpose temperature and/or pressure responsive means are used for actuating valves which reverse the flow of pressure fluid in the conduits normally supplying pressure fluid conduits connected to the servomotors which conduits are controlled by the return motion pilot valves when the temperatures and/ or pressures of the resuperheated steam are below predetermined values so that the respective throttle means is closed irrespective of the output of the respective b'oiler or of the position of the respective distributing device.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself however and additional objects and advantages thereof will best be understood from the following description of embodiments thereof when read in connection with the accompanying drawing in which Figs. 1a and 1b diagrammatically illustrate a control system according to the invention;

Figure 2. is a simplified diagrammatic illustration of a modified control system.

Like parts are designated by like numerals in all Figures of the drawing.

Referring more particularly to the drawing, letters A, B, and C designate steam generators including superheaters a, b, and 0, respectively, and delivering superheated steam into a steam main 1 which conducts the steam into a high pressure turbine 2, forming part of a turbine plant which drives, for example, an electric generator G. The exhaust of the high pressure turbine 2 is conducted through a pipe line 3 into resuperheaters 4, 5, and 6 which are combined and heated together with the steam generators A, B, and C, respectively. The steam resuperheated in the resuperheaters 4, 5, and 6 is conducted through pipes 7, 8, and 9 into a conduit 13 wherefrom the steam flows into a low pressure turbine 14 and, if desired, to other steam consumers, not shown. The pipes 7, 8, and 9 are provided with throttle valves 93, 94, and 95, respectively, for controlling the relative amounts of steam flowing through the resuperheaters. The steam exhausting from the turbine plant 2, 14 is condensed in a condenser 15. The condensate is conducted through a pipe 16 into a feed water container 17 from which it is conducted through a conduit 18 to feed pumps 19, 20, and 21 for the steam generators A, B, and C, respectively. Between each feed pump and the respective steam generator a feed water control valve 22, 23, 24, respectively, is arranged.

The valves 22, 23, 24 are controlled by feed water regulators 45, 46, 47, respectively. These regulators are illustrated diagrammatically only, the illustrations representing a suitable example. The regulators may be replaced by other suitable and conventional devices. Since all three regulators are alike only one will be described. Each of the valves 22, 23, and 24 has a valve stem 200 which is actuated through a lever 201 by means of a float 202 in dicating the water level in the boilers A, B, C. Each valve stem is provided with a rack 203 engaging a toothed wheel 204 on whose shaft a cam 205 is mounted. The latter engages a cam follower roller 205 connected by a spring 206 with a pilot valve piston 207 for the boiler A, with a piston 208 for the boiler B, and with a piston 209 for the boiler C.

The pistons 207, 208, 209 control the flow of a pressure fluid into and out of conduits 48, 50, and 52, respectively. The cam 205 is so shaped that the control pressure or signal produced by the respective piston is a function of the logarithm of the load on the respective boiler, i.e., the amount of steam produced by the respective boiler.

The system according to the invention includes a distributing or controlling device for each resuperheater, device 31 being associated with the resuperheater 4, device 32 being associated with the resuperheater 5, and

device 33 being associated with the resuperheater 6. The devices 31, 32, 33 individually include step pistons 210, 211, 212, respectively. Each piston is reciprocable in a correspondingly shaped stepped cylinder. One side of the piston 210 is provided with two steps 82 and 83; one side of the piston 211 is provided with two steps 89, and one side of the piston 212 is provided with two steps 91, 92. The number of steps of each step piston is one less than the number of resuperheaters served by the system according to the invention. If there are six boilers and six resuperheaters, there are six step pistons, each having five steps. The area of all steps is the same.

Conduit 48 conducts pressure fluid to and from the step 90 of the step piston 211 pertaining to the reheater 5 and through an extension conduit 49 to and from the step 92 of the step piston 212 which pertains to the reheater 6.

Conduit 50 conducts pressure fluid to and from the step 82 of the step piston 210 which is associated with the resuperheater 4 and through an extension conduit 51 with the step 91 of the step piston 212 which is associated with the reheater 6.

Conduit 52 conducts pressure fluid to and from the step 89 of the step piston 211 which pertains to the resuperheater 5 and, through an extension conduit 53, to the step 83 of the piston 210 which pertains to the resuperheater 4.

The step pistons 210, 211, 212 individually have trunk portions 213, 214, 215, respectively, forming valves for controlling the flow of a pressure fluid from a source, not shown, into and out of main pressure fluid conduits 34, 35, and 36, respectively. The fluid in the latter takes part in the control of the flow of a pressure fluid to and from servomotors for actuating throttle valves 93, 94, 95, respectively. With the devices shown by way of" example in Figure l the total pressure acting on the steps of the distributing piston for the resuperheater which is associated with the highest loaded boiler is smaller than the total pressure acting on the steps of any of the other distributing pistons. The total pressure acting on the steps of the other step pistons is the higher the smaller the amount of steam produced by the related boilers relatively to the amount of steam produced by the highest loaded boiler. If, for example, the total pressure acting on the steps of a step piston increases due to decreasing relative steam output of the respective boiler, the step piston will be moved upward (from its middle position. The pilot valve forming part of this particular step piston will relieve pressure fluid from the connected rn-ain pressure fluid conduit causing closing of the respective resuperheater throttle valve.

To each pressure fluid conduit 34, 35, 36 a compensating device 37, 38, 39, respectively, is connected. These devices include pilot valves whose valve pistons 84, 85, 86, respectively, are moved by the pressure in the conduits 34, 35, 36 against springs 215, 216, 217, respectively. The pilot valves 84, 85, 86 are interposed in series relation in a compensating pressure fluid supply conduit 40, 41, and control the flow of pressure fluid through conduits 42, 43, 44 to the top of the distributing pistons 210, 211, 212, respectively, counteracting the pressures acting on the steps of the pistons.

Since the upper chambers of the step cylinders of the distributing or controlling devices 31, 32, 33 are connected in parallel relation with respect to the flow of pressure fluid through the conduit 40, 41, the pressure in all three step cylinders is the same. The pressure fluid regulating valve 37 is connected to a source of supply of pressure fluid, not shown. The valve 38 receives pressure fluid from the valve 37 through the conduit 40 and the valve 39 receives pressure fluid through conduit 41 from the valve 38. Each of the valves 37, 38, 39 is provided with an outlet for relieving pressure fluid when the valve piston is above its middle position. The springs 215, 216, 217 are so adjusted that the respective pilot valves are in middle or neutral position, in which no pressure fluid flows through the valves, when the pressure in the respective main pressure fluid conduits is sufliciently high to fully open the respective resuperheater throttle valve. When the pressure in a main pressure fluid conduit drops below a predetermined value the respective compensating pilot valve moves below its middle position, opening the valve to pressure fluid flow.

If none of the conduits 34, 35, 36 carries a pressure at which the respective throttle valve is fully open, the compensating pilot valves are all below their neutral positions so that pressure fluid flows through the valve 37 into the conduit 40 and therefrom through the valve 38 into conduit 41 and continues to flow through the valve 39 into the conduits 42, 43, and 44 and onto the upper surfaces 81, 87, and 88 of the distributing pistons 210, 211, and 212, pressing the latter downward. This causes admission of pressure fluid into the main pressure fluid conduits 34, 35, and 36 until the pressure in one of the conduits which pertains to the resuperheater associated with the hi hest loaded boiler reaches the maximum control value at which the respective throttle valve is fully open. This causes movement of the respective compensating pilot valve into its neutral position, interrupting flow of pressure fluid onto the surfaces 81, 87, and 88.

If the pressure in the main control conduit pertaining to the boiler producing most steam rises beyond the maximum control value because of relatively lower output of the other boilers, the compensating valve pertaining to the highest loaded boiler moves upward beyond its middle position, relieving pressure fluid, while the compensating valves pertaining to the less loaded boilers remain below their middle positions so that the passage therethro-ugh is open. This causes a drop of pressure on all surfaces 81, 87, and 88 and a rising of the pistons 210, 211, 212 so that pressure fluid is withdrawn from or less fluid flows into the main conduits 34, 35, 36 until the pressure in one of the conduits is again equal to the predetermined maximum control value.

If, of the three boilers of the illustrated example, only two are in operation, the system operates in a similar manner. The boiler carrying the greater load produces the control pressure at which the pertaining resuperheater throttle valve is fully opened. The difference between the maximum control pressure and the control pressure produced by the less loaded boiler corresponds to the diflerence between the loads carried by the two boilers.

If only one boiler is in operation, the respective distributing device will always produce the control pressure at which the throttle valve of the resuperheater associated with the boiler which is in operation is fully open irrespective of the amount of steam produced by the boiler.

Each of the throttle valves 93, 94, 95 is actuated by a servomotor or motor operator 96, 97, 90, respectively, including a piston on one side of which acts the fluid pressure supplied through conduits 114, 115, 116, respectively. On the other side of each servomotor piston is a spring counteracting the fluid pressure. The pressure fluid side of each servomotor cylinder is provided with a threaded spindle which can be manipulated by means of a hand wheel 218, 219, 220, respectively, for defining the extreme positions of each valve and for manually opening and closing the valves.

The fluid supply to the servomotor-s or motor operators 96, 97, 98 is controlled by pilot valves 99, 100, 101, respectively, from conduits 64, 78, 80, respectively, which will be described later. The pilot valves 99, 100, 101 contain valve pistons 102, 103, 104, respectively. On the bottom of the valve pistons act the pressures provided by the main control pressure conduits 34, 35, 36 against the pressures of springs 221, 222, 223, respectively, which act on the top of the pistons. The tension of the 107, respectively, which are linked to two-arm levers 111, 112, 113, swinging on pivots 108, 109, 110, respectively, and are pivoted to and actuated by the spindles of the throttle valves 93, 94, 95. v

A manually operable three-way valve 132, 133, 134 is provided on each pilot valve 99, 100, 101, respectively, for diverting pressure fluid from the pilot valves and cutting the valves 011 the main pressure fluid conduits 34, 35, 36. A second manually operable three-way valve 135, 136, 137, respectively, is provided in each conduit 34, 35, 36 for supplying pressure fluid into the main control conduits and actuating the pilot valves 99, 100, 101 and servomotors and throttle valves connected therewith independently of the distributing devices 31, 32, 33.

The cams 105, 106, 107, forming part of return motions, are so shaped as to compensate the flow resistance of the valves, the respective resuperheaters, and pipe lines connected therewith at various throttle valve openings and amounts of steam flowing through the resuperheaters so that the valve openings are always so that amounts of steam pass through the respective resuperheaters whose ratios to the amounts of steam produced by the respective boilers are equal to the ratio of the total amount of steam flowing through all resuperheaters to the total amounts of steam produced by the boilers.

The cams 105, 106, 107 may also be so shaped as to compensate for the varying heat transfer conditions in the individual resuperheaters at different loads. The amount of steam supplied to a resuperheater of a less loaded boiler should be smaller than at an exactly proportional distribution whereas the amount of steam sup plied to the resuperheater of the highest loaded boiler must be relatively greater. These deviations from the proportional distribution are the greater the smaller the ratio between the amount of steam produced by the less loaded boiler to the amount of steam produced by the boiler carrying the greatest load.

The system illustrated by Way of example includes also means for preventing discharge of steam from the resuperheaters into the medium pressure steam line and turbine or turbines supplied thereby Whenthe resuperheater does not have the desired pressure and/or temperature. Each of the pipe lines 7, 8, 9 extending from the resuperheaters 4, 5, and 6, respectively, is connected with a pressure sensitive device 62, 75, 76 by means of a pipe 63, 73, 74, respectively. Furthermore, each pipe line 7, 8, 9 is provided with a thermostat 57, 67, 68, respectively.

The pressure sensitive devices 62, 75, 76 actuate pilot valves 117, 118, 119, respectively, for controlling the flow of a pressure fluid from a source, not shown, into and out of conduits 61, 77, 78, respectively. The fluid pressure in the conduits 61, 77, 78 actuate pilot valves 120, 121, 122, respectively.

The thermostats 57, 67, 68 actuate pilot valves 58, 65, 66, respectively, for controlling the flow of a pres sure fluid from a source, not shown, into and out of conduits 59, 69, 70, respectively. The fluid pressure in the conduits 59, 69, 70 actuates pilot valves 126, 127, 128, respectively.

The valves 126, 127, 128 control the flow of pressure fluid from a source, not shown, into and out of conduits 129, 130, 131, connecting the valves 126, 127, 128 with the valves 120, 121, 122, respectively. The latter valves control the flow of pressure fluid into and out of coinduits 64, 78, 80 which supply pressure fluid through the control valves 99, 100, 101 to the servo-motors 96, 97, 98, respectively.

If the resuperheaters deliver steam of the desired pressure and temperature, the pilot valve pistons 120, 121, 122 and 126, 127, 128 are in their upper positions and admit pressure fluid to the control valves 99, 100, 101, respectively. If the pressure and/or temperature is too low, one or both of the valve pistons 120, 126 or 121, 127 or 122, 128 drops down, interrupting the supply of pressure fluid to the control valves 99, 100, and 101 or even relieving pressure fluid therefrom.

If a boiler must be shut down, the respective resuperheater throttle valve can be closed by manupulating the respective three-way valve 132, 133, or 134 so that the contiguous valve 99, 100, or 101 moves into the position in which pressure fluid is relieved from the respective servomotor piston. If only one boiler is in operation, the throttle valves of the resuperheaters associated with the other boilers are closed by diverting pressure fluid from the respective control valves by manipulating the contiguous three-way valves. The throttle valve of the resuperheater associated with the boiler which is in operation is fully open as long as the resuperheater delivers steam of the desired pressure and temperature.

In the example illustrated in Fig. l the boiler A produces most steam while the boilers B and C are less loaded. Therefore the valve piston of the compensating device 37 is in its middle position whereas the pistons 35 and 86 of the devices 38 and 39 pertaining to the boilers B and C are below middle position. The throttle valve 93 of the resuperheater associated with the boiler A is fully open whereas the throttle valves 94 and 95 of the resuperheaters associated with boilers B and C are less wide open. If, for example, the load on boiler B is increased while the load on boilers A and C remains unchanged, the fluid pressure in the conduits 50 and 51, produced by the feed water regulator 46, rises and more pressure is exerted on the steps 82 and 91 of the distributing devices 31 and 33. This causes a lowering of the pressures in the conduits 34 and 36. The piston 84 of the compensating device 37 descends and the piston 86 of the compensating device 39 is still more lowered. The conduits 40 and 41 are therefore supplied with pressure fluid which passes onto the surfaces 81, 87, and 88 of the distributing step pistons, depressing the latter and causing an increase of the control pressures in the conduits 34, 35, 36. This goes on until the distributing device 31 pertaining to the still highest loaded boiler A reaches the value at which the throttle valve 93 is fully open. This pressure returns the valve 84 to its middle position, interrupting further supply of pressure fluid to the surfaces 81, 87, 88. Whereas the control pressures produced by the distributing devices 31 and 33 pertaining to the boilers A and C are back to their previous values, the control pressure produced by the distributing device 32 has become greater. Consequently, the throttle valve 94 of the resuperheater has been opened farther, in proportion to the increased load on the boiler B.

Fig. 2 illustrates a system in which the resuperheater throttle valves are placed at the inlets of the resuperheaters and in which the control of the throttle valves in response to the pressure and temperature of the resuperheated steam is omitted. The distributing system is actuated by conventional steam flow meters 225, 226, 227, which measure the amounts of useful steam produced by the boilers A, B, C, respectively. These flow meters replace the water level indicators on which the control system shown in Fig. 1 is based and actuate devices 207, 208, 209, respectively, corresponding to the devices designated by the same niunerals in Fig. 1. The fluid controlled by the devices 207, 208, 209 actuates the distributing devices 31, 32, 33 which control the fluid pressure in the main control conduits 34, 35, 36 to which oompensating means 37, 38, 39 are connected, all in the same manner as shown in Fig. 1.

The system according to the invention assures correct distribution of steam into a plurality of resuperheaters at any combination of loads on the boilers with which the resuperheaters are associated. The system operates satisfactorily also at very low loads and is applicable to natural circulation boilers as well as to forced circulation boilers operating at subcritical or supercritical pressure.

The individual elements of the system are conventional and may be replaced by equivalent pneumatic, hydraulic, or electric elements producing the same result.

What is claimed is:

l. A steam generating and resuperheating apparatus including at least three steam generators, a source of heat connected with each of said steam generators, a steam resuperheater connected to each of said steam generators and being heated by the respective source of heat, a throttle means connected to each of said resuperheaters for controlling the flow of steam to be resuperheated through the individual resuperheaters, and a control apparatus connected to said throttle means for actuating the latter to effect a relative steam flow through the individual resuperheaters which corresponds to the relative rates of output of the respective steam generators and to fully open the throttle of the resuperheater connected to the steam generator operating at the highest output rate, said control apparatus comprising a control signal producing means connected to each of said steam generators for individually producing control signals corresponding to the rate of output of the respective steam generator, at controlling means for each resuperheater, sa d controlling means being individually connected to d signal producing means with the exception of the signal producing means connected to the steam generator to which the respective resuperheater is connected, said controlling means individually including means for addingthe signals received from the connected signal producing means for individually producing control pulses corresponding to the sum of the signals produced by the signal producing means of the steam generators which are not connected to tor operator connect tter and including pilot means 0 eratively connected to the controlling means of the r:

spect ve resuperheater for effecting individual actuation of said motor operators in response to the control pulses produced by the respective controlling means, a pressure flu1d, a conduit for said pressure fluid connected to each of said controlling means, means to actuate each of the latter by the pressure fluid in opposition to the action of said control signals, and a pressure fluid regulating valve for each of said controlling means, said valves being interposed in series relation in said pressure fluid conduit and individually including valve opening means for yieldably holding the valves in open position, said valves individually including means individually operatively connected to said controlling means and being responsive to the control pulses produced by the respective controlling means for closing the respective valve against the action of said opening means when the respective control pulse reaches a value effecting full opening of the re- 5136201126 throttle means.

steam generating and resu erheatin a as defined in claim 1 wherein said riontrol a npai zi t uis iifi cludes temperature responsive pulse producing means individually connected to the steam outlets of said resuperheaters for producing additional control pulses corre sponding to the temperature of the resuperheated steam, said temperature responsive means being individually operatively connected to the pilot means of the respective motor operators for actuating the latter supplementally to the actuation in response to the control pulses produced by the respective controlling means, for inhibiting opening of the respective throttle means, if the temperature of the reheated steam is below a predetermined value.

3. A steam generating and resuperheating apparatus as defined in claim 1 wherein said control apparatus includes pressure responsive pulse producing means individually connected to said resuperheaters for producing additional control pulses corresponding to the pressure of the resuperheated steam, said pressure responsive the respective resuperheater, a mo-' means being individually operatively connected to the pilot means of the respective motor operators for actuating the latter supplementally to the actuation in response to the control pulses produced by the respective controlling means, for inhibiting opening of the respective throttle means, if the pressure in the reheater is below a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 

